Volume fracturing three-dimensional development method suitable for unconventional multi-layer gas reservoir horizontal well

Abstract

The invention relates to the technical field of well drilling and fracturing of horizontal wells, in particular to a volume fracturing three-dimensional development method suitable for unconventional multi-layer gas reservoir horizontal wells, which comprises the following steps of: 1, drilling a well by adopting a phi 331.2 mm drill bit to form a surface phi 331.2 mm well hole (11) with the surface well depth (14), and 2, carrying out volume fracturing on a first well body structure suitable for a first horizontal well of which the horizontal section is less than 1200m; and 2, a surface casing (12) with the diameter phi being 244.5 mm is put into the well hole (11) with the diameter phi being 331.2 mm. According to the method, after the first well is exploited and exhausted, a phi152.4 mm casing pipe is adopted for sidetrack drilling in a phi177.8 mm technical casing pipe or a well completion casing pipe, a phi114.3 mm well completion casing pipe can be put down to meet the volume fracturing requirement, the reserved phi177.8 mm technical casing pipe is used for gas production, external power tools such as an electric submersible pump and a screw pump can be put down, the recovery efficiency is improved, and the well completion casing pipe can be put down to meet the volume fracturing requirement. Meanwhile, an old well site, a ground pipeline and an upper casing pipe are recycled, and the investment cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of horizontal well drilling and fracturing, and is a volume fracturing three-dimensional development method suitable for horizontal wells of unconventional multi-layer gas reservoirs. Background Art

[0002] In the same block, tight oil and gas fields and coal-bed methane have multiple reservoirs vertically developed. The use of horizontal well volume fracturing can greatly increase production and recovery. However, horizontal wells can generally only develop a single reservoir. If multiple reservoirs are developed vertically, a new horizontal well can only be drilled (such as Figure 1 , 1 is drilling rig 1, 2 is horizontal well bore 2, 3 is drilling rig 3, 4 is horizontal well bore 4, 5 is non-gas reservoir formation 5, 6 is unconventional gas reservoir 6, 7 is non-gas reservoir formation 7, 8 is unconventional gas reservoir 8, 9 is non-gas reservoir formation 9), the surface casing and technical casing of the first horizontal well cannot be reused, which will greatly increase the investment; it is necessary to innovate a new wellbore structure, which can drill a horizontal well in the first well after the first well reservoir is exhausted, so as to achieve the same efficient development effect as the first well. Such as: horizontal well development, volume fracturing, drainage gas production, etc. The surface casing, technical casing, ground pipe network, etc. of the first well can also be reused.

[0003] At present, horizontal wells usually adopt a single wellbore structure, such as: a single φ139.7mm / φ127mm / φ114.3mm completion casing is run from the wellhead to the bottom of the well. After the first well is exhausted, if side drilling is carried out, only the casing below the φ89mm oil pipe can be run to complete the well. Due to the small diameter of the pipe, the conditions for volume fracturing are not met, and efficient development cannot be achieved. Summary of the invention

[0004] The present invention provides a volume fracturing three-dimensional development method suitable for horizontal wells in unconventional multi-layer gas reservoirs, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problem of increased costs caused by the inability to reuse the surface casing and technical casing of the existing first horizontal well.

[0005] The technical solution of the present invention is achieved by the following measures: A volume fracturing three-dimensional development method for horizontal wells in unconventional multi-layer gas reservoirs is carried out according to the following steps: Applicable to the first wellbore structure of the first horizontal well with a horizontal section less than 1200m: Step 1: Drilling with a φ331.2 mm drill bit to form a surface φ331.2 mm wellbore (11) with a surface well depth of (14); Step 2: lowering a φ244.5 mm surface casing (12) into a φ331.2 mm wellbore (11); Step 3: injecting surface casing cementing cement (13) between the φ331.2 mm wellbore (11) and the φ244.5 mm casing (12); Step 4: Drilling with a φ222.3 mm drill bit to form a φ222.3 mm wellbore (21), with a completed well depth of (24); Step 5: lowering a φ177.8 mm completion casing (221) and a φ139.7 mm completion casing (222) into the φ222.3 mm wellbore (21), and injecting completion casing cementing cement (23) between the φ222.3 mm wellbore (21) and the φ177.8 mm completion casing (221) and the φ139.7 mm completion casing (222); Step 6: Performing horizontal well volume fracturing operations in the φ177.8 mm completion casing (221) and the φ139.7 mm completion casing (222); Applicable to the second wellbore structure of the first horizontal well with a horizontal section greater than 1200m: Step 1: Drilling with a φ331.2 mm drill bit to form a surface φ331.2 mm wellbore (11) with a surface well depth of (14); Step 2: lowering a φ244.5 mm surface casing (12) into a φ331.2 mm wellbore (11); Step 3: injecting surface casing cementing cement (13) between the φ331.2 mm wellbore (11) and the φ244.5 mm casing (12); Step 4: Drilling with a φ222.3 mm drill bit to form a φ222.3 mm wellbore (21), with a completed well depth of (35); Step 5: lowering a φ177.8 mm technical casing (22) into a φ222.3 mm wellbore (21); Step 6: injecting technical casing cementing cement (23) between the φ222.3 mm wellbore (21) and the φ177.8 mm technical casing (22); Step 7: Drilling with a φ152.4 mm drill bit to form a φ152.4 mm wellbore (31), with a completed well depth of (34); Step 8: inserting a delivery drill pipe (46), a hanger (36), and a φ114.3 mm completion casing (32) into the φ177.8 mm technical casing (22) and the φ152.4 mm wellbore (31), injecting completion cement (33) between the φ177.8 mm technical casing (22), the φ152.4 mm wellbore (31), and the φ114.3 mm completion casing (32), and removing the delivery drill pipe (46); Step 9: Run the φ114.3 mm tieback casing (37); Step 10: Performing a horizontal well volume fracturing operation in a φ114.3 mm tieback casing (37), a hanger (36), and a φ114.3 mm completion casing (32); Step 11: After fracturing, the φ114.3 mm tieback casing (37) is removed. The φ177.8 mm technical casing (22) has a large diameter and can be used for sidetracking. Sidetracking of the first wellbore structure and the second wellbore structure: Step 1: Select the side drilling point (45); Step 2: Backfill cement (40) below the side drilling point (45) to block the unconventional gas reservoir (8); Step 3: Use a φ152.4 mm whipstock to side-drill from a φ177.8 mm completion casing (221) or a φ177.8 mm technical casing (22) side-drilling point (45), use a φ152.4 mm drill bit to drill, side-drill in the unconventional gas reservoir (6) to form a φ152.4 mm wellbore (41), and the completion depth is (44); Step 4: inserting a delivery drill pipe (46), a hanger (47), and a φ114.3 mm completion casing (42) into a φ177.8 mm completion casing (221) or a φ177.8 mm technical casing (22) and a side-drilled φ152.4 mm wellbore (41), injecting cement (43) between the φ177.8 mm completion casing (221) or the φ177.8 mm technical casing (22) and the side-drilled φ152.4 mm wellbore (41) below the hanger (47), injecting cement (43) between the φ114.3 mm completion casing (42) and the side-drilled φ152.4 mm wellbore (41), and pulling out the delivery drill pipe (46); Step 5: A φ114.3 mm tieback casing (48) is lowered, and the φ114.3 mm tieback casing (48) is connected to a φ114.3 mm completion casing (42) via a hanger (47); Step 6: Performing horizontal well volume fracturing operations in a φ114.3 mm tieback casing (48), a hanger (47), and a φ114.3 mm completion casing (42); Step 7: After fracturing, the tieback casing (48) is pulled out. Above the hanger (47) is a φ177.8 mm completion casing (221) or a φ177.8 mm technical casing (22), which has a large diameter and can also be used for side drilling.

[0006] The following are further optimizations and / or improvements to the above technical solutions: In the first wellbore structure, in step 5, the lower end of the φ177.8 mm completion casing (221) is connected to the φ139.7 mm completion casing (222) via a φ177.8 mm casing female buckle and a φ139.7 mm casing male buckle short section (25).

[0007] In the above-mentioned second wellbore structure, in step 9, the φ114.3 mm tieback casing (37) is connected to the φ114.3 mm completion casing (32) via a hanger (36).

[0008] In the side-drilling step 1 of the first wellbore structure and the second wellbore structure, the side-drilling point selection method is that the well section with good quality of the completion casing cementing cement (23) outside the φ177.8mm technical casing (22) and the side-drilling well deflection section is ≤5.5° / 30m.

[0009] According to the method of the present invention, when the first well is exhausted, after side drilling with a φ152.4mm casing in a φ177.8mm technical casing or a completion casing, a φ114.3mm completion casing can be lowered to meet the volume fracturing requirement. During the gas production process of the reserved φ177.8mm technical casing, an electric submersible pump, a screw pump and other external power tools can be lowered to improve the recovery rate. At the same time, the old well site, the ground pipeline and the upper casing are reused to reduce the investment cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Attached Figure 1 It is a schematic diagram of the background technology structure.

[0011] Attached Figure 2 It is a schematic diagram of the three-dimensional development structure of horizontal wells in unconventional multi-layer gas reservoirs according to the present invention.

[0012] Attached Figure 3 Schematic diagram of the φ177.8mm casing structure reserved above the reservoir for the composite casing second opening wellbore structure.

[0013] Attached Figure 4 Schematic diagram of the drill pipe being sent into the φ114.3mm completion casing structure after side drilling of the composite casing secondary wellbore structure.

[0014] Attached Figure 5 This is a schematic diagram of the composite casing secondary wellbore structure in which the drill pipe is fed into the φ114.3mm completion casing and then connected back to the φ114.3mm casing structure.

[0015] Attached Figure 6 Schematic diagram of the φ177.8mm completion casing structure reserved for connecting back to the φ114.3mm casing after fracturing.

[0016] Attached Figure 7 Diagram of sending φ114.3mm completion casing into the drill pipe for hanging cementing three-opening wellbore structure.

[0017] Attached Figure 8 In order to suspend and cement the three-opening wellbore structure, the drill pipe is sent in and the φ114.3mm casing structure is connected back.

[0018] Attached Fig. 9 Schematic diagram of the φ177.8mm completion casing structure reserved for the suspension cementing three-opening wellbore structure after fracturing and the back-connection of the φ114.3mm casing.

[0019] Attached Fig.10 Schematic diagram of the structure of φ114.3mm completion casing after side drilling for the suspended cementing three-opening wellbore structure.

[0020] Attached Fig.11 Schematic diagram of the structure of the suspended cementing three-opening well body after side drilling, the drill pipe is put in and the φ114.3mm casing is connected back.

[0021] Attached Fig.12 Schematic diagram of the structure of the suspended cementing three-opening wellbore, in which a φ114.3mm casing is proposed for connection after side drilling and fracturing, and a φ177.8mm completion casing is reserved. DETAILED DESCRIPTION

[0022] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0023] In the present invention, for the convenience of description, the relative position relationship of each component is described according to the attached Figure 1 The positional relationships such as front, back, top, bottom, left, and right are described according to the layout directions of the drawings in the specification.

[0024] The present invention will be further described below in conjunction with embodiments and drawings: Embodiment 1: As attached Figures 2 to 12 As shown, the volume fracturing three-dimensional development method for horizontal wells in unconventional multi-layer gas reservoirs is carried out according to the following steps: Applicable to the first wellbore structure of the first horizontal well with a horizontal section less than 1200m: Step 1: Drilling with a φ331.2 mm drill bit to form a surface φ331.2 mm wellbore (11) with a surface well depth of (14); Step 2: lowering a φ244.5 mm surface casing (12) into a φ331.2 mm wellbore (11); Step 3: injecting surface casing cementing cement (13) between the φ331.2 mm wellbore (11) and the φ244.5 mm casing (12); Step 4: Drilling with a φ222.3 mm drill bit to form a φ222.3 mm wellbore (21), with a completed well depth of (24); Step 5: lowering a φ177.8 mm completion casing (221) and a φ139.7 mm completion casing (222) into the φ222.3 mm wellbore (21), and injecting completion casing cementing cement (23) between the φ222.3 mm wellbore (21) and the φ177.8 mm completion casing (221) and the φ139.7 mm completion casing (222); Step 6: Performing horizontal well volume fracturing operations in the φ177.8 mm completion casing (221) and the φ139.7 mm completion casing (222); Applicable to the second wellbore structure of the first horizontal well with a horizontal section greater than 1200m: Step 1: Drilling with a φ331.2 mm drill bit to form a surface φ331.2 mm wellbore (11) with a surface well depth of (14); Step 2: lowering a φ244.5 mm surface casing (12) into a φ331.2 mm wellbore (11); Step 3: injecting surface casing cementing cement (13) between the φ331.2 mm wellbore (11) and the φ244.5 mm casing (12); Step 4: Drilling with a φ222.3 mm drill bit to form a φ222.3 mm wellbore (21), with a completed well depth of (35); Step 5: lowering a φ177.8 mm technical casing (22) into a φ222.3 mm wellbore (21); Step 6: injecting technical casing cementing cement (23) between the φ222.3 mm wellbore (21) and the φ177.8 mm technical casing (22); Step 7: Drilling with a φ152.4 mm drill bit to form a φ152.4 mm wellbore (31), with a completed well depth of (34); Step 8: inserting a delivery drill pipe (46), a hanger (36), and a φ114.3 mm completion casing (32) into the φ177.8 mm technical casing (22) and the φ152.4 mm wellbore (31), injecting completion cement (33) between the φ177.8 mm technical casing (22), the φ152.4 mm wellbore (31), and the φ114.3 mm completion casing (32), and removing the delivery drill pipe (46); Step 9: Run the φ114.3 mm tieback casing (37); Step 10: Performing a horizontal well volume fracturing operation in a φ114.3 mm tieback casing (37), a hanger (36), and a φ114.3 mm completion casing (32); Step 11: After fracturing, the φ114.3 mm tieback casing (37) is removed. The φ177.8 mm technical casing (22) has a large diameter and can be used for sidetracking. Sidetracking of the first wellbore structure and the second wellbore structure: Step 1: Select the side drilling point (45); Step 2: Backfill cement (40) below the side drilling point (45) to block the unconventional gas reservoir (8); Step 3: Use a φ152.4 mm whipstock to side-drill from a φ177.8 mm completion casing (221) or a φ177.8 mm technical casing (22) side-drilling point (45), use a φ152.4 mm drill bit to drill, side-drill in the unconventional gas reservoir (6) to form a φ152.4 mm wellbore (41), and the completion depth is (44); Step 4: inserting a delivery drill pipe (46), a hanger (47), and a φ114.3 mm completion casing (42) into a φ177.8 mm completion casing (221) or a φ177.8 mm technical casing (22) and a side-drilled φ152.4 mm wellbore (41), injecting cement (43) between the φ177.8 mm completion casing (221) or the φ177.8 mm technical casing (22) and the side-drilled φ152.4 mm wellbore (41) below the hanger (47), injecting cement (43) between the φ114.3 mm completion casing (42) and the side-drilled φ152.4 mm wellbore (41), and pulling out the delivery drill pipe (46); Step 5: A φ114.3 mm tieback casing (48) is lowered, and the φ114.3 mm tieback casing (48) is connected to a φ114.3 mm completion casing (42) via a hanger (47); Step 6: Performing horizontal well volume fracturing operations in a φ114.3 mm tieback casing (48), a hanger (47), and a φ114.3 mm completion casing (42); Step 7: After fracturing, the tieback casing (48) is pulled out. Above the hanger (47) is a φ177.8 mm completion casing (221) or a φ177.8 mm technical casing (22), which has a large diameter and can also be used for side drilling.

[0025] The new wellbore structure must be able to run in φ60.3mm or 48.3mm production tubing after fracturing, and in the later stage of gas production, external power drainage gas production tools can be run in; after the first well is exhausted, horizontal well sidetracking can be carried out in the original wellbore, and the diameter of the horizontal well completion casing after sidetracking is ≥114.3mm, and the fracturing displacement is ≥8m³ / min. Therefore, φ177.8mm technical casing or completion casing needs to be reserved in the vertical well section.

[0026] The present invention provides a first horizontal well to complete the development of a reservoir, conduct horizontal well drilling, fracturing, and gas production, reserve a φ177.8mm completion casing or technical casing above the reservoir, and when the natural gas production of the first well is exhausted, close the first reservoir from below the side drilling point. Side drilling is performed from the reserved φ177.8mm completion casing or technical casing to produce the second reservoir, and a completion string that meets the requirements of horizontal well volume fracturing is lowered to perform fracturing, gas production and other processes. If there is a third reservoir, it can be developed in sequence, thereby realizing the three-dimensional development of horizontal well volume fracturing of unconventional multi-layer gas reservoirs. Since horizontal well volume fracturing can be achieved each time, the single well fracturing transformation process can be maximized, and the purpose of increasing production and single well cumulative production can be finally achieved. The well site, ground pipeline and upper casing of the old well can also be used to minimize investment. A φ177.8mm technical casing or completion casing is reserved for each development, which is conducive to the lowering of external power tools such as electric submersible pumps and screw pumps during gas production to improve the recovery rate.

[0027] Compared with the prior art, the present invention has the following advantages: 1. Starting from gas production and fracturing, the wellbore structure is optimized, which is suitable for the development of different reservoirs in unconventional multi-layer gas reservoirs and for the entire life cycle of unconventional multi-layer gas reservoirs; 2. It can realize the three-dimensional development of unconventional multi-layer gas reservoirs in the same wellbore at different times. Each layer can be subjected to horizontal well volume fracturing, and the maximum program fracturing can be used to transform the reservoir to obtain the maximum production and recovery rate; 3. During the gas production process, φ177.8mm technical casing or completion casing is reserved. When the reservoir is exhausted, another reservoir can be developed by side drilling at the side drilling point to form a horizontal well with volume fracturing capability; 4. The φ114.3mm casing for tieback can be reused, which greatly saves production and construction investment; 5. One well site, surface casing, technical casing or completion casing, and ground pipeline can be used multiple times, greatly saving investment; 6. When one reservoir is exhausted, production succession can be achieved by developing the second and third reservoirs through side drilling.

[0028] According to actual needs, the above-mentioned volume fracturing three-dimensional development method for horizontal wells in unconventional multi-layer gas reservoirs can be further optimized and / or improved: Embodiment 2: As attached Figure 3 As shown, in the first wellbore structure, in step 5, the lower end of the φ177.8 mm completion casing (221) is connected to the φ139.7 mm completion casing (222) via a φ177.8 mm casing female buckle and a φ139.7 mm casing male buckle short section (25).

[0029] Embodiment 3: As attached Figure 7 , 8As shown in FIG. 9 , in the second wellbore structure, in step 9, the φ114.3 mm tieback casing (37) is connected to the φ114.3 mm completion casing (32) via a hanger (36).

[0030] Embodiment 4: As attached Figure 4 , 5 As shown in , 6, 10, 11, and 12, in step 1 of side drilling of the first wellbore structure and the second wellbore structure, the side drilling point selection method is that the well section with good quality of the completion casing cementing cement (23) outside the φ177.8mm completion casing (221) or the φ177.8mm technical casing (22), and the dogleg degree of the side drilling well deflection section is ≤5.5° / 30m.

[0031] Example 5: Using a composite casing two-opening wellbore structure, with a φ177.8mm casing reserved above the reservoir It is suitable for the first horizontal well with a horizontal section less than 1200m. Its advantages are short drilling cycle and large fracturing displacement.

[0032] Step 1( Figure 3 ): Drilling is carried out using a φ331.2 mm drill bit to form a surface φ331.2 mm wellbore 11, and the surface well depth is 14; Step 2( Figure 3 ): A φ244.5 mm surface casing 12 is lowered into a φ331.2 mm wellbore 11; Step 3( Figure 3 ): inject surface casing cementing cement 13 between the φ331.2mm wellbore 11 and the φ244.5mm casing 12; Step 4 Figure 3 ): Drilling was performed using a φ222.3 mm drill bit to form a φ222.3 mm wellbore 21 in the unconventional gas reservoir 8, and the completion depth was the second opening completion depth 24; Step 5 Figure 3 ): A φ177.8mm completion casing 221+φ139.7mm completion casing 222 is lowered into a φ222.3mm wellbore 21, and the φ177.8mm completion casing 221 and the φ139.7mm completion casing 222 are connected by a φ177.8mm casing female buckle*φ139.7mm casing male buckle short section 25; Step 6 Figure 3 ): injecting completion casing cementing cement 23 between the φ222.3mm wellbore 21 and the φ177.8mm completion casing 221 + φ139.7mm completion casing 222; Step 7 Figure 3 ): Perform horizontal well volume fracturing operations in φ177.8mm completion casing 221+φ139.7mm completion casing; Step 8: The φ177.8mm completion casing 221 has a large diameter and can be used for side drilling.

[0033] Composite casing secondary wellbore structure side drilling to achieve multi-layer reservoir horizontal well volume fracturing three-dimensional development Unconventional natural gas wells are generally produced by exhaustion. When the natural gas in the unconventional gas reservoir is exhausted, the old well casing can be used for side drilling.

[0034] Step 1( Figure 4 ): Select the side drilling point: φ177.8mm completion casing 221, external completion casing cementing cement 23, good quality well section; the dogleg degree of the side drilling well deflection section is ≤5.5° / 30m, and the side drilling point is 45; Step 2( Figure 4 ): Backfill cement 40 below the side drilling point 45 to block the unconventional gas reservoir 8; step( Figure 4 )3: Use a φ152.4mm whipstock to side-drill from the side-drilling point 45, use a φ152.4mm drill bit to drill, form a φ152.4mm wellbore 41 in the unconventional gas reservoir 6, and complete the drilling to a depth of 44; Step 4 Figure 4 ): Run the delivery drill pipe 46 + hanger 47 + φ114.3mm completion casing 42 into the reserved φ177.8mm completion casing 221 + φ152.4mm wellbore 41, inject cement 43 between the hanger 47 and the φ114.3mm completion casing 42 in the reserved φ177.8mm completion casing 221 + φ152.4mm wellbore 41, and pull out the delivery drill pipe 46; Step 5 Figure 5 ): Run the φ114.3mm tieback casing 48; Step 6 Figure 5 ), performing horizontal well volume fracturing operation in φ114.3 mm tieback casing 48 + hanger 47 + φ114.3 mm completion casing 42; Step 7 Figure 6 ): After fracturing, the tieback casing 48 is brought out, and above the hanger 47 is a φ177.8mm completion casing and a φ177.8mm technical casing 5, which has a large diameter and can also be used for side drilling.

[0035] Example 6: Using a suspended cementing three-opening wellbore structure, with a φ177.8mm casing reserved above the reservoir It is suitable for the first horizontal well with a horizontal section greater than 1200m. It has the advantage of a long horizontal section and can be used in stable reservoirs or barrier areas to increase the controlled reserves of a single well.

[0036] Step 1( Figure 7): Drilling is carried out using a φ331.2 mm drill bit to form a surface φ331.2 mm wellbore 11, with a surface well depth of 14; Step 2( Figure 7 ): A φ244.5 mm surface casing 12 is lowered into a φ331.2 mm wellbore 11; Step 3( Figure 7 ): inject surface casing cementing cement 13 between the φ331.2mm wellbore 11 and the φ244.5mm casing 12; Step 4 Figure 7 ): Drilling is performed using a φ222.3mm drill bit to form a φ222.3mm wellbore 21, the middle completion depth is 35, and a φ177.8mm technical casing 22 is run into the φ222.3mm wellbore 21; Step 5 Figure 7 ): injecting intermediate cement 23 between the φ222.3mm wellbore 21 and the φ177.8mm technical casing 22; Step 6 Figure 7 ): Drilling with a φ152.4 mm drill bit to form a φ152.4 mm wellbore 31 in the unconventional gas reservoir 8; Step 7 Figure 7 ): Run the delivery drill pipe 46 + hanger 47 + φ114.3mm completion casing 32 into the φ177.8mm technical casing 22 + φ152.4mm wellbore 31, inject completion cement 33 between the φ177.8mm technical casing 22 + φ152.4mm wellbore 31 and the φ114.3mm completion casing 32, and pull out the delivery drill pipe 46; Step 8 Figure 8 ): Run the φ114.3mm tieback casing 37; Step 9 Figure 8 ), performing horizontal well volume fracturing operation in φ114.3mm tieback casing 37+hanger 47+φ114.3mm completion casing 32; Step 10 Fig. 9 ): After fracturing, the tieback casing 37 is brought out, and above the hanger 47 is a φ177.8mm completion casing and a φ177.8mm technical casing 5, which has a large diameter and can be used for side drilling.

[0037] Suspended cementing three-opening wellbore structure side drilling, realizing multi-layer reservoir horizontal well volume fracturing three-dimensional development ( Fig.10 , Fig.11 , Fig.12 ) When the natural gas in the unconventional gas reservoir 8 is exhausted, the old well φ177.8mm technical casing can be used for side drilling.

[0038] Step 1( Fig.10): Select the side drilling point: φ177.8mm technical casing 22, external completion casing cementing cement 23, good quality well section; the dogleg degree of the side drilling well deflection section is ≤5.5° / 30m, and the side drilling point is 45; Step 2( Fig.10 ): Backfill cement 40 below the side drilling point 45 to block the unconventional gas reservoir 8; Step 3( Fig.10 ): A φ152.4 mm whipstock was used to side-drill from the side-drilling point 45, and a φ152.4 mm drill bit was used to drill the well. A φ152.4 mm wellbore 41 was formed by side-drilling in the unconventional gas reservoir 6, and the well was completed to a depth of 44; Step 4 Fig.10 ): Run the delivery drill pipe 46 + hanger 47 + φ114.3mm completion casing 42 into the reserved φ177.8mm technical casing 22 + side-drilled φ152.4mm wellbore 41, inject cement 43 between the φ114.3mm completion casing 42 and the hanger 47 in the reserved φ177.8mm technical casing 22 + side-drilled φ152.4mm wellbore 41, and pull out the delivery drill pipe 46; Step 5 Fig.11 ): Run the φ114.3mm tieback casing 48; Step 6 Fig.12 ), performing horizontal well volume fracturing operation in φ114.3 mm tieback casing 48 + hanger 47 + φ114.3 mm completion casing 42; Step 7 Fig.12 ): After fracturing, the tieback casing 48 is brought out, and above the hanger 47 is a φ177.8mm completion casing and a φ177.8mm technical casing 5, which has a large diameter and can also be used for side drilling.

[0039] Example 7: Surface casing, technical casing, and completion casing models (1) Optimal casing selection for composite casing secondary wellbore structure (2) Suspended cementing three-opening well body structure Example 8: Horizontal well volume fracturing method and construction parameters In the case of this wellbore structure, staged fracturing technologies such as pumping bridge plugs, continuous tubing dragging, and cementing sleeves can be used to achieve horizontal well volume fracturing.

[0040] The volume fracturing parameters are as follows: It can be seen from the above table that both completion strings can meet the need for volume fracturing of more than 8m³ / min before sidetracking. Therefore, both completion strings can meet the need for fracturing displacement ≥ 8m³ / min after sidetracking.

[0041] Example 9: Supporting unconventional gas reservoir drainage gas production method Unconventional natural gas wells are generally characterized by low pressure, low permeability, water content, and rapid decline. Drainage and gas production are the key to increasing production and recovery. The following table shows the minimum liquid carrying flow rate of API oil pipe gas wells of different specifications.

[0042] (1) In order to reduce the critical liquid carrying flow rate of the gas well and take into account the friction resistance of gas production, φ60.3mm or φ48.3 production tubing is generally selected; (2) When the production of a natural gas well drops to 110% of the critical liquid-carrying flow rate, take drainage and gas production measures in advance to reduce pressure loss and extend the stable production period. Such measures include: foam drainage, plunger, etc. (3) When measures such as bubble drainage and plunger are ineffective, and liquid accumulates in the production string and the annulus between the production string and the completion casing, making it impossible to produce normally, a φ177.8 mm casing with a large diameter is reserved at the top, so an electric submersible pump, screw pump, etc. can be lowered into the casing, and external power is used to force drainage to increase the cumulative production and recovery rate of the gas well.

[0043] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A three-dimensional development method for horizontal well volume fracturing in unconventional multi-layer gas reservoirs, characterized in that This includes following these steps: Applicable to the first wellbore structure of the first horizontal well with a horizontal section less than 1200m: Step 1: Drilling with a φ331.2 mm drill bit to form a surface φ331.2 mm wellbore (11) with a surface well depth of (14); Step 2: lowering a φ244.5 mm surface casing (12) into a φ331.2 mm wellbore (11); Step 3: injecting surface casing cementing cement (13) between the φ331.2 mm wellbore (11) and the φ244.5 mm casing (12); Step 4: Drilling with a φ222.3 mm drill bit to form a φ222.3 mm wellbore (21), with a completed well depth of (24); Step 5: lowering a φ177.8 mm completion casing (221) and a φ139.7 mm completion casing (222) into the φ222.3 mm wellbore (21), and injecting completion casing cementing cement (23) between the φ222.3 mm wellbore (21) and the φ177.8 mm completion casing (221) and the φ139.7 mm completion casing (222); Step 6: Performing horizontal well volume fracturing operations in the φ177.8 mm completion casing (221) and the φ139.7 mm completion casing (222); Applicable to the second wellbore structure of the first horizontal well with a horizontal section greater than 1200m: Step 1: Drilling with a φ331.2 mm drill bit to form a surface φ331.2 mm wellbore (11) with a surface well depth of (14); Step 2: lowering a φ244.5 mm surface casing (12) into a φ331.2 mm wellbore (11); Step 3: injecting surface casing cementing cement (13) between the φ331.2 mm wellbore (11) and the φ244.5 mm casing (12); Step 4: Drilling with a φ222.3 mm drill bit to form a φ222.3 mm wellbore (21), with a completed well depth of (35); Step 5: lowering a φ177.8 mm technical casing (22) into a φ222.3 mm wellbore (21); Step 6: injecting technical casing cementing cement (23) between the φ222.3 mm wellbore (21) and the φ177.8 mm technical casing (22); Step 7: Drilling with a φ152.4 mm drill bit to form a φ152.4 mm wellbore (31), with a completed well depth of (34); Step 8: inserting a delivery drill pipe (46), a hanger (36), and a φ114.3 mm completion casing (32) into the φ177.8 mm technical casing (22) and the φ152.4 mm wellbore (31), injecting completion cement (33) between the φ177.8 mm technical casing (22), the φ152.4 mm wellbore (31), and the φ114.3 mm completion casing (32), and removing the delivery drill pipe (46); Step 9: Run the φ114.3 mm tieback casing (37); Step 10: Performing a horizontal well volume fracturing operation in a φ114.3 mm tieback casing (37), a hanger (36), and a φ114.3 mm completion casing (32); Step 11: After fracturing, the φ114.3 mm tieback casing (37) is removed. The φ177.8 mm technical casing (22) has a large diameter and can be used for sidetracking. Sidetracking of the first wellbore structure and the second wellbore structure: Step 1: Select the side drilling point (45); Step 2: Backfill cement (40) below the side drilling point (45) to block the unconventional gas reservoir (8); Step 3: Use a φ152.4 mm whipstock to side-drill from a φ177.8 mm completion casing (221) or a φ177.8 mm technical casing (22) side-drilling point (45), use a φ152.4 mm drill bit to drill, side-drill in the unconventional gas reservoir (6) to form a φ152.4 mm wellbore (41), and the completion depth is (44); Step 4: inserting a delivery drill pipe (46), a hanger (47), and a φ114.3 mm completion casing (42) into a φ177.8 mm completion casing (221) or a φ177.8 mm technical casing (22) and a side-drilled φ152.4 mm wellbore (41), injecting cement (43) between the φ177.8 mm completion casing (221) or the φ177.8 mm technical casing (22) and the side-drilled φ152.4 mm wellbore (41) below the hanger (47), injecting cement (43) between the φ114.3 mm completion casing (42) and the side-drilled φ152.4 mm wellbore (41), and pulling out the delivery drill pipe (46); Step 5: A φ114.3 mm tieback casing (48) is lowered, and the φ114.3 mm tieback casing (48) is connected to a φ114.3 mm completion casing (42) via a hanger (47); Step 6: Performing horizontal well volume fracturing operations in a φ114.3 mm tieback casing (48), a hanger (47), and a φ114.3 mm completion casing (42); Step 7: After fracturing, the tieback casing (48) is pulled out. Above the hanger (47) is a φ177.8 mm completion casing (221) or a φ177.8 mm technical casing (22), which has a large diameter and can also be used for side drilling.

2. The method for volume fracturing and three-dimensional development of horizontal wells in unconventional multi-layer gas reservoirs according to claim 1, characterized in that In the first wellbore structure, in step 5, the lower end of the φ177.8 mm completion casing (221) is connected to the φ139.7 mm completion casing (222) via a φ177.8 mm casing female buckle and a φ139.7 mm casing male buckle short joint (25).

3. The method for volume fracturing and three-dimensional development of horizontal wells in unconventional multi-layer gas reservoirs according to claim 1, characterized in that In the second wellbore structure, in step 9, the φ114.3 mm tieback casing (37) is connected to the φ114.3 mm completion casing (32) via a hanger (36).

4. The method for volume fracturing and three-dimensional development of horizontal wells in unconventional multi-layer gas reservoirs according to claim 1, 2 or 3, characterized in that In step 1 of side drilling of the first wellbore structure and the second wellbore structure, the side drilling point selection method is that the well section of the φ177.8 mm completion casing (221) or the φ177.8 mm technical casing (22) outside the completion casing cementing cement (23) is of good quality, and the dogleg degree of the side drilling well deflection section is ≤5.5° / 30m.

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